Guideline References

One-Stage Prothrombin Time (PT) Test and Activated Partial Thromboplastin Time (APTT) Test

H47-A2 requires that the ISI and Normal Patient Mean PT be correctly programmed into the coagulation analyzer and verified after each reagent lot change. The INR calculation — INR = (PT / Normal Patient Mean PT)^ISI — must be implemented correctly in the analyzer's software.

Standard: Establishment and Verification of Method Performance Specifications

Requires laboratories to verify that instrument-reported values are accurate and that calibration parameters are correctly configured. For PT/INR, this includes confirming that ISI and NPM programming is correct before reporting patient results.